Although micromachining techniques for silicon are well developed and a range of silicon MEMs have been fabricated, Si MEMs are not suitable for use in harsh environments including locations of high temperature, high vibrational frequency, high wear and those containing corrosive media. In contrast, silicon carbide (SiC) is an excellent material for microsensors and microactuators for use in extreme conditions due to its outstanding physical and chemical properties. In particular, because of the high Young's modulus (E) of SiC and the relatively low-mass density ρ the larger ratio of √{square root over (E/ρ)} will result in significantly higher resonant frequencies for SiC beam structures compared to their silicon and gallium arsenide counterparts.
Micromachined SiC resonant devices including pressure sensors, lateral resonant structures and micromotors are known. However, most of the fabricated devices make use of bulk micromachining or micromolding techniques that tend to be more complex than surface micromaching. Significant bending effects have also been observed in released cantilever beams, especially in longer beam structures. The bending effect has been attributed to the result of a bending moment induced by a residual stress gradient through the film thickness, the presence of the mask and the surface tension encountered in wet etch processes. In addition, compared with dry etching techniques, there is also less control of etch rates and etch profiles using wet etch to release resonance structures.